Roland Piquepaille's Technology Trends
How new technologies are modifying our way of life

dimanche 11 avril 2004

Scientists at the National Institute of Standards and Technology (NIST) have created magnetic "tweezers" that let them manipulate individual biomolecules. This article from NIST Tech Beat, Controlling Biomolecules With Magnetic 'Tweezers', says it will help them to study "folding patterns and other biochemical details important in medical, forensic and other research areas."

An array of magnetic traps designed for manipulating individual biomolecules and measuring the ultrasmall forces that affect their behavior has been demonstrated by scientists at the National Institute of Standards and Technology (NIST).
The chip-scale, microfluidic device works in conjunction with a magnetic force microscope. It’s intended to serve as magnetic "tweezers" that can stretch, twist and uncoil individual biomolecules such as strands of DNA.
The new NIST device works like drawing toys that use a magnetized stylus to pick up and drag magnetic particles. Magnetic particles 2 to 3 micrometers across are suspended in a fluid and injected into the device. The surface of a thin membrane enclosing the fluid is dotted with an array of thin film pads made of a nickel-iron alloy. When a magnetic field is applied, each particle is attracted to the closest nickel-iron "trap."
Concept of magnetic trap Here is a diagram showing the "concept of magnetic trap for single-magnetic-bead manipulation in a microfluidic cell. Bio-molecules will be attached to the beads for single-molecule manipulation and measurements" (Credit: Nanoprobe Imaging Project).

This research work was published by Applied Physics Letters on March 8, 2004 (Vol 84(10) pp. 1786-1788). Here is the abstract of this paper, "Integrated microfluidic isolation platform for magnetic particle manipulation in biological systems."

We have developed a micromachined fluid-cell platform that consists of patterned magnetic thin-film elements supported on a thin silicon–nitride membrane. In the presence of an external magnetic field, the field gradients near the magnetic elements are sufficiently large to trap magnetic particles that are separated from the patterned films by a 200 nm thick nitride membrane. The two main applications of this fluid-cell platform are to provide a means to control and position magnetic microparticles, which can be tethered to biological molecules, and also to sort superparamagnetic microparticles based on their size and magnetic susceptibility. We determine the characteristic trapping forces of each trap in the array by measuring the Brownian motion of the microparticle as a function of applied external field. Typical force constants and forces on the superparamagnetic particles are 4.8×10–4±0.7×10–4 N/m and 97±15 pN, respectively.

Sources: NIST Tech Beat, April 9, 2004; and various websites

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